Pigmented plastics

ABSTRACT

Compositions containing pigment, cellulose triacetate, and small amounts of high boiling solvents are prepared for use as concentrates for coloring cellulose triacetate solutions prior to spinning of yarns and filaments from the solution.

United States Patent 1 Sonn et al. 1 1 Jan. 8, 1974 1 PIGMENTED PLASTICS2,544,363 3/1951 Siemens 106/193 J 2,761,789 9/1956 Locher'et aL 106/193D [751 inventor-SI Geprge Frank 9"" Edlson; Frank 3,554,114 1/1911115111118151". J; roe/1'96 Michael McGonlgle, South Plainfield, both ofNJ.

[73] Assignee: lnmont Corporation, New York, im ry i ert Gant N.Y.Assistant Examiner-S. Berger 1 [22] Filed: June 1971 Attorney-F. W.Wyman and P. Al'VldSOI] [211 App]. No.: 148,979

52 us. c1. 1015/2880, 1116/1915 J, 106/193 P, [57] ABSTRACT 106/196,106/309 v [51] Int. Cl C08h 17/02 Compositions containing pigment,cellulose triacetate, [58] Field of Search..., 106/288 0, 308 Q, ndsmall amounts of high'boiling solvents are pre- 106/309, 193 J, 193 P,193 D, 193 M, 196 pared for use as concentrates for coloring cellulosetriacetate solutions prior to spinning of yarns and fila [56] ReferencesCited 7 ments from the solution.

UNITED STATES PATENTS v 2,701.21 1 2/1955 Taylor'et al; 106/193 D 7Claims, N0 Drawings PIGMENTED PLASTICS This invention relatestopigmented cellulose triacetate compositions. More particularly, theinvention relates to a method for the production of pigmented cellulosetriacetate compositions suitable for spinning of yarns andfilaments.

In the spinning of yarns or filaments from solutions of cellulosetriacetate whereinpigments are dispersed in the solution to color theresulting yarns, it has been difficult to obtain adequate dispersion ofthe pigment in the spinning solution, or dope, by conventional methods.A major problem'has been that the pigment is not broken down to a fineenough particle size to pass through thespinrierts.

The present invention provides a method for dispersing pigments incellulose triacetate solutions which greatly alleviates the aboveproblem. In accordance with the'invention a concentrate premix is firstprepared comprising a relatively high percentage of pigment, cellulosetriacetate, and a mixture of high boiling and low boiling solvents, byconventional mixing as in a sigma blade type dough mixer until all lumpsare broken up and the mixture isuniformly blended. The premix is thenmilled on an open plastic milling device such as a two roll mill untilthe mixture begins to blister and does notstick to the rolls. Themixture is removed from the mill, pulverized, and used to colorsolutions of cellulose triacetate prior to spinning or extruding thesolution to form fibers or filaments. The concentrated premix of pigmentand plastic can be uniformly dispersed in the cellulose triacetatespinning solution by simple mixing such as by using a paddle mixer withslow agitation. In a preferred embodiment of the invention secondarycellulose acetate, up to an amount equal to the cellulose triacetate,can be used in the premix. The resulting concentratedpigment'dispersions generally contain to 60 percent pigment, 2 to 12percent solvent, and to 60 percent cellulose triacetate or mixture ofthe triacetate and secondary acetate.

A test that is suitable for determining whether the concentrates pigmentdispersion can be used to pigment cellulose triacetate spinningsolutions consists of measuring the filterability of the concentratedispersion. In the filterability test a 700 gram sample of thedispersion is adjusted to 8 percent solids by addition of a solventmixture consisting of IO'percent methanol and 90 methylene chloride. Thediluted dispersion is then filtered through a standard filter cloth discunder 200 PSI nitrogen pressure. The filterability may be expressed ingrams or in percentage. Thus, if all of the dispersion filters throughthe filter the filterability is 700 grams or 100 percent. Dispersionshaving a filterability of 250 grams or higher are operable forpigmenting cellulose triacetate spinning solutions.

The pigment dispersions must be usuable in the spinning or extrudingprocess without appreciably affecting the resulting fiber or filamentexcept to color it.

Secondary cellulose acetate, as used herein, means cellulose acetatehaving 52 percent to 56 percent acetyl groups, of combined acetic acidby weight. These secondary acetates are available on the market invarious grades and viscosities and anyof these can be used in thepresent invention.

High boiling volatile solvents, as used herein, means volatile solventsthat have boiling points on the order of about 100C. and above. Thesesolvents must be 501- vents for cellulose triacetate, and when mixedwith low boiling solvents the mixture should be a solvent forcellulosetriacetate. Also, when secondary cellulose acetate is used inmaking the concentrate, these high boiling solvents alone, and inmixtures: with the low boiling solvent, must be a solvent for secondarycellulose acetate. Suitable solvents include: diacetone alcohol, methylpyrolidone, isophorone, cyclohexanone, and triacetin (glyceroltriacetate) Diacetone alcohol is especially preferred because of itssolvency properties and also because of economy, its odor and lowtoxicity.

Low boiling volatile solvents, as used herein, means volatile solventsfor cellulose triacetate and secondary cellulose acetate, at least inmixtures with the high boiling solvent, that having a boiling point onthe order of about 35C to about C. Suitable solvents include: acetone,methyl acetate, ethyl acetate, methyl ethyl ketone, methylene chloride,etc. Acetone is especially preferred because of economy, ease ofhandling, and toxicological considerations.

It should be noted that the real limitation as to the 'mixture ofsolvents employed in the invention is whether or not the mixture is asolvent for cellulose triacetate, or a mixture of cellulose triacetateand secondary acetate. Those skilled in the art can readily appre ciatethat it is possible to predict which combinations of solvents will beoperable based on solubility parameters and hydrogen bonding propertiesof the solvents. For instance, it is known that cellulose triacetate andsecondary acetate are soluble in poor hydrogen bonding solvents havingsolubility parameters of the order of 9 to 13. Low hydrogen bondingsolvents include: aliphatic and aromatic solvents, chlorinatedhydrocarbons and nitrohydrocarbons. Similarly, it is known thatcellulose triacetate and secondary acetate are soluble in moderatelyhydrogen bonded solvents having solubility parameters of the order of9.5 to 9.9 for cellulose triacetate and 9.0 to 13 for secondary acetate.Moderately hydrogen bonded solvents include, for example, esters, ethersand ketones. Also, it is know that cellulose triacetate and secondarycellulose acetate are soluble in strongly hydrogen bonded solventshaving solubility parameters of the order of 10.0 to 10.8. Stronglyhydrogen bonded solvents include amides, alcohols, amines and acids.Finally, it can also be noted that mixtures of solvents whose individualsolubility parameters may be outside the above ranges can be solventsfor cellulose triacetate and secondary acetate if the mixture has theproper solubility parameter. For instance, methanol which has asolubility parameter of 14.5 can be used with methylene chloride,solubility parameter of 9.7 to dissolve cellulose triacetate.

Pigments that can be used in the invention include those or organicnature such as phthalocyanine blue, phthalocyanine green, quinacridones,perylene tetracarboxylic acid di-imides, dioxazines, perinones disazopigments and anthraquinone pigments. Also inorganic pigments can beused, e.g., carbon black, titanium dioxide, metal powders, iron oxideand ultramarine. Mixtures of two or more pigments can, of course beused. The pigment must, of course, be stable to the heat used in thespinning process. Preferably the concentrate contains 25 to 60 percentpigment.

Other conventional additives may be included in either the concentratepigment dispersion or the spinning dope if desired. Such additivesinclude optical brighteners, softening agents, stablizers, etc.

During the plastic milling of the premix on an open mill, most of themore volatile solvent contained in the dispersion evaporates. It isbelieved that this gradual evaporation of solvent during milling of thedispersion contributes greatly to the high degree of dispersionobtained. However, evaporation of volatile solvent is not the onlyfactor responsible because, using the highly volatile solvent alonewithout using any high boiling solvent, the high degree of dispersionobtainable by the invention are not obtainable. On the other hand,milling of the concentrate in the absence of the low boiling, highlyvolatile solvent, does not give the desirable results of the invention.If desired, additional small portions of solvent mixture, or smallportions of low boiling solvent can be added during milling to obtainimproved processing on the two roll mill.

The following examples in which the parts are by weight are given tofurther illustrate the invention.

The above ingredients were premixed in a sigma blade dough mixer untiluniform and then milled on a 2-roll rubber mill until it began toblister and would no longer stay on the rolls. The resulting dispersioncontained 48 percent pigment, by weight, 24 percent cellulosetriacetate, 24 percent secondary cellulose acetate, and 4 percentsolvent consisting essentially of diacetone alcohol. The filterabilityof the dispersion was 300 grams. The dispersion was useful to pigmentcellulose triacetate spinning dopes prior to extrusion into fibers; itwas readily and uniformly blended with the dope by simple paddle mixingin any desired ratio of, for example, up to parts of concentrate to 90parts of dope, without adversely affecting fiber properties. Cellulosetriacetate solutions containing percent to percent by weight ofcellulose triacetate are generally used for spinning.

Example 2 Parts Phthalocyanine Blue 34.8 Cellulose triacetate 18.1Secondary acetate 18.1 Triacetin, B. P. 258C. 12.0 Methyl acetate, B. P.57C. 17.0

Example 3 Parts Carbon Black 34.8 Cellulose triacetate 34.2 Methylpyrrolidone 8.0 Ethyl acetate, B. P. 77C. 23.0

The above ingredients were premixed and milled as in Example 1 to obtaina concentrate dispersion containing about 48 percent carbon black, 48percent triacetate and 4 percent solvent consisting essentially ofmethyl pyrrolidone. The dispersion had a filterability of 450 grams andwas useful to pigment cellulose triacetate spinning dopes prior toextrusion into fibers.

It will be understood that the practice of the invention is not limitedto the dispersions described in the specific examples, but that variousmodifications may be made therein without departing from the scope ofthe invention as it is defined in the appended claims.

What is claimed is:

1. A process for preparing concentrated pigment dispersions suitable forpigmenting cellulose triacetate spinning solution, said processingcomprising 1 forming a premix comprised of pigment, cellulose triacetateor a mixture of cellulose triacetate with up to an equal amount ofsecondary cellulose acetate, and volatile solvent in an amountsufficient to enable the premix to be milled on an open plastic millingmachine, said volatile solvent consisting of a mixture of volatilesolvent having a boiling point within the range of about 35C to C, andvolatile solvent having a boiling point above C, and (2) plastic millingthe premix on an open mill until it begins to blister and no-longeradhers to the mill, to form said dispersion consisting essentially of 25to 60 percent pigment, 2 to 12 percent solvent and 30 to 60 percentcellulose triacetate or mixture of cellulose triacetate and up to anequal amount of secondary cellulose acetate.

2. A process as in claim l'which includes a final step of pulverizingthe dispersion.

3. A process as in claim 1 wherein secondary cellulose acetate isincluded in the premix up to an amount equal to the amount of cellulosetriacetate.

4. A process as in claim 3 which includes a final step of pulverizingthe dispersion.

5. A process for preparing concentrate pigment dispersions suitable forpigmenting cellulose triacetate spinning solutions, said processcomprising 1 forming a premix comprised of pigment, cellulose triacetateor a mixture of cellulose triacetate with up to an equal amount ofsecondary cellulose acetate, and volatile solvent in an amountsufficient to enable the premix to be milled on an open plastic millingmachine, said volatile solvent consisting of a mixture of volatilesolvent having a boiling point within the range of about 35C. to 95C.,and high boiling solvent having a boiling point above 100C, and (2)plastic milling the premix on an open mill until substantially all ofthe low boiling solvent evaporates and the resulting dispersion has afilterability of at least 250 grams, said dispersion consistingessentially of 25 to 60 percent pigment, 2 to 12 percent solvent and 30to 60 percent cellulose triacetate or mixture of cellulose triacetateand up to an equal amount of secondary cellulose acetate.

6. A process as in claim 5 wherein secondary cellulose acetate isincluded in the premix up to an amount equal to the amount of cellulosetriacetate.

7. A process as in claim 6 which includes a final step of pulverizingthe dispersion.

2. A process as in claim 1 which includes a final step of pulverizingthe dispersion.
 3. A process as in claim 1 wherein secondary celluloseacetate is included in the premix up to an amount equal to the amount ofcellulose triacetate.
 4. A process as in claim 3 which includes a finalstep of pulverizing the dispersion.
 5. A process for preparingconcentrate pigment dispersions suitable for pigmenting cellulosetriacetate spinning solutions, said process comprising (1) forming apremix comprised of pigment, cellulose triacetate or a mixture ofcellulose triacetate with up to an equal amount of secondary celluloseacetate, and volatile solvent in an amount sufficient to enable thepremix to be milled on an open plastic milling machine, said volatilesolvent consisting of a mixture of volatile solvent having a boilingpoint within the range of about 35*C. to 95*C., and high boiling solventhaving a boiling point above 100*C., and (2) plastic milling the premixon an open mill until substantially all of the low boiling solventevaporates and the resulting dispersion has a filterability of at least250 grams, said dispersion consisting essentially of 25 to 60 percentpigment, 2 to 12 percent solvent and 30 to 60 percent cellulosetriacetate or mixture of cellulose triacetate and up to an equal amountof secondary cellulose acetate.
 6. A process as in claim 5 whereinsecondary cellulose acetate is included in the premix up to an amountequal to the amount of cellulose triacetate.
 7. A process as in claim 6which includes a final step of pulverizing the dispersion.